Thioarsenates in Geothermal Waters of Yellowstone National Park: Determination, Preservation, and Geochemical Importance

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• 作者：Britta Planer-Friedrich ; Jacqueline London ; R. Blaine McCleskey ; D. Kirk Nordstrom ; Dirk Wallschl&auml ; ger
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：August 1, 2007
• 年：2007
• 卷：41
• 期：15
• 页码：5245 - 5251
• 全文大小：210K
• 年卷期：v.41,no.15(August 1, 2007)
• ISSN：1520-5851

文摘

Mono-, di-, tri-, and tetrathioarsenate, as well asmethylated arsenic oxy- and thioanions, were determinedbesides arsenite and arsenate in geothermal waters ofYellowstone National Park using anion-exchange chromatography inductively coupled plasma mass spectrometry.Retention time match with synthetic standards, measuredS:As ratios, and molecular electrospray mass spectrasupport the identification. Acidification was unsuitable forarsenic species preservation in sulfidic waters, with HCladdition causing loss of total dissolved arsenic, presumablyby precipitation of arsenic-sulfides. Flash-freezing ispreferred for the preservation of arsenic species for severalweeks. After thawing, samples must be analyzedimmediately. Thioarsenates occurred over a pH range of2.1 to 9.3 in the geothermal waters. They clearly predominatedunder alkaline conditions (up to 83% of total arsenic),but monothioarsenate also was detected in acidic waters(up to 34%). Kinetic studies along a drainage channelshowed the importance of thioarsenates for the fate ofarsenic discharged from the sulfidic hot spring. The observedarsenic speciation changes suggest three separatereactions: the transformation of trithioarsenate to arsenite(major initial reaction), the stepwise ligand exchangefrom tri- via di- and monothioarsenate to arsenate (minorreaction), and the oxidation of arsenite to arsenate,which only becomes quantitatively important afterthioarsenates have disappeared.